1. Field of the Invention
The present invention relates to an improved method for effecting water control during treating of subterranean zones in wells utilizing aqueous well treating fluids.
2. Description of the Prior Art
High viscosity aqueous crosslinked gels are used in a variety of operations and treatments carried out in subterranean zones or formations including, but not limited to, production stimulation treatments.
An example of a production stimulation treatment utilizing a high viscosity crosslinked gelled fluid is hydraulic fracturing. In hydraulic fracturing treatments, the high viscosity fluid is utilized as a fracturing fluid and also carries particulate propping agent, such as, sand, into the fractures formed. That is, the fracturing fluid is pumped through the wellbore into a formation to be stimulated at a rate and pressure such that fractures are formed and extended in the formation. Propping agent is suspended in the fracturing fluid so that it is deposited in the fractures when the gel is broken and returned to the surface. The propping agent functions to prevent the formed fractures from closing whereby conductive channels are formed through which produced fluids can flow to the wellbore.
Borate ion has long been used as a crosslinking agent for forming high viscosity crosslinked gelled well treating fluids. Various sources of borate ion have been utilized including boric acid, borax, sodium tetraborate and proprietary compositions comprised of boric acid and dimers and trimers of borate ions. Additionally, titanium, zirconium, aluminum, antimony ions and the like have been used as crosslinking agents to form high viscosity crosslinked gelled fluids.
A problem that often occurs during the performance of a stimulation treatment in an oil or gas producing zone which contains high permeability streaks which produce water or is subject to water influx is stimulation of the water producing zones concurrently with stimulation of the oil production. In such instances, water production from the formation may be excessive, requiring expensive separation and water disposal. Alternatively, after a stimulation treatment has been performed, a water control treatment may be attempted to reduce the production of water. The remedial treatments are expensive and are not always successful. The treatments can result in plugging of the formation and loss of production.
It would be desirable to provide a means by which a formation may be treated to selectively reduce the permeability of a subterranean formation to water flow while not damaging the ability of oil to flow through the formation to the producing well.